UV-activated chlorination process

ABSTRACT

A method of producing alkanes containing chlorine by addition of chlorine to C—C double bonds or C—C triple bonds or by exchange of hydrogen for chlorine by contacting the starting compound in the gas or liquid phase with elemental chlorine and irradiating the reaction mixture with UV light having a wavelength of λ≧280 nm. In this way pentachloroethane can be produced from trichloroethylene, CFC-113 from HCFC-123 or HFC-133a, CFC-112a from HCFC-142b, or HCFC-123 from HCFC-133a. The method also is suitable for separating photochlorinatable impurities from HFC-365-mfc to obtain purified HFC-365-mfc. Advantages include high yields and excellent selectivity.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of international patentapplication no. PCT/DE00/01953, filed Jun. 14, 2000 designating theUnited States of America, the entire disclosure of which is incorporatedherein by reference. Priority is claimed based on Federal Republic ofGermany patent application no. DE 199 27 394.4, filed Jun. 16, 1999.

BACKGROUND OF THE INVENTION

[0002] The invention relates to a process for producing certainchlorine-containing alkanes through UV-light supported chlorination.

[0003] It has long been known that elemental chlorine under incidentlight radiation will attach to unsaturated carbon compounds or that anexchange of hydrogen for chlorine will occur.

SUMMARY OF THE INVENTION

[0004] It is an object of the invention to provide a new process forproducing chlorine-containing alkanes.

[0005] Another object of the invention is to provide a process forproducing chlorine-containing alkanes with a high reaction rate and highselectivity.

[0006] These and other objects are achieved in accordance with thepresent invention as described and claimed hereinafter.

[0007] The process according to the invention for producingchlorine-containing alkanes selected from the group consisting ofpentachloroethane, 1,1,1,-trifluoro-2,2,2-trichloroethane,1,1,1-trifluoro-2,2-dichloroethane and1,1,1,2-tetrachloro-2,2-difluoroethane by attaching chlorine to startingcompounds with C—C double bonds or by exchanging hydrogen for chlorine,and for producing purified 1,1,1,3,3-pentafluorobutane from1,1,1,3,3-pentafluorobutane that has been contaminated with compoundswith C—C double bonds or C—C triple bonds by chlorinating theseunsaturated compounds, provides that the starting compound in the gas orthe liquid phase is brought into contact with elemental chlorine and isirradiated with UV light with a wavelength of λ≧280 nm.

[0008] It is possible to work in the liquid phase or in the gas phase.Generally, one can work at a temperature ranging from room temperatureto 200° C. and at a pressure of 1 to 10 bar (absolute). The reactiontemperature and the pressure are selected in such a way that thestarting compound to be treated, or the starting mixture, is present inthe gas phase or the liquid phase. One variant of the invention concernsits use as a production process. Another variant concerns its use as apurification process. The use as a production process will first bedescribed in greater detail.

[0009] Particularly preferably, the process is used to producepentachloroethane from trichloroethylene, to produce1,1,1,2-tetrachloro-2,2-difluoroethane from 1-chloro-1,1-difluoroethane,and to produce 1,1,1-trifluoro-2,2,2-trichloroethane from1,1,1-trifluoro-2,2-dichloroethane.

[0010] The molar ratio of starting compound to elemental chlorine rangesfrom 1:0.1 to 1:10 when attaching chlorine and from 1:0.01 to 1:5 whenexchanging hydrogen for chlorine. If only one of two H atoms is to beexchanged in the exchange of hydrogen for chlorine, the ratio ofstarting compounds to chlorine falls in the upper range (lower chlorinecontent). Preferably, the chlorine is used in an amount that is 0.9times to 1.3 times the stoichiometrically required amount.

[0011] Another variant of the invention concerns the purification of1,1,1,3,3-pentafluorobutane (HFC-365mfc) with the aim of separatingphotochlorinatable olefinic impurities. It has been shown that theolefinic impurities, which are production-related, can essentially beselectively converted by the inventive photochlorination and separatedin a simplified manner in the form of chlorination products.

[0012] For irradiation, it is advantageous to use radiation lamps (e.g.,Philips fluorescent tubes) that only emit (UV) light of a wavelength ator above 280 nm (λ≧280 nm). In such case, it is possible to irradiatethrough quartz glass. The only prerequisite for this variant is thatthese lamps emit in the absorption range of the elemental chlorine.Alternatively, it is possible to use radiation lamps (e.g., Hg medium orhigh-pressure discharge lamps), which also emit some lines in the rangebelow 280 nm (λ<280 nm). In this variant, irradiation has to occurthrough a glass that is transparent only for light with a wavelength of280 nm or above (λ>280=n), i.e., that filters out the shorter waveradiation component of λ<280 nm. Well suited are, for instance,borosilicate glasses. This type of glass typically contains 7 to 13%B₂O₃, 70 to 80% SiO₂, furthermore 2 to 7% Al₂O₃ and 4 to 8% Na₂O+K₂O and0 to 5% alkaline-earth metal oxides. Known trademarks for borosilicateglasses are Duran, Pyrex and Solidex. It is of course also possible toproceed by using on the one hand a radiation lamp that emits light abovethe indicated wavelengths and, in addition, glasses that are transparentfor light above the indicated wavelength (i.e., that are non-transparentfor light below the indicated wavelength).

[0013] Also suitable for irradiation are lamps, e.g., Hg high-pressuredischarge lamps, which due to a dopant emit primarily, or only, in thewavelength range at or above 280 nm. Hg high-pressure discharge lamps,for instance, have a rather intensive band in the range of 254 nm whichis filtered out, e.g., by borosilicate glass, as described above. In Hghigh-pressure discharge lamps that are doped with metal iodides, thisline is strongly suppressed. Surprising in these doped lamps is thefrequently more than proportional increase in the conversion rate.Excellent results with respect to conversion rate and selectivity areobtained with Hg high-pressure discharge lamps that are doped withgallium iodide and especially with lamps that are doped with thalliumiodide or cadmium iodide. Even with the use of this type of lamp, it ispreferable to use glass that filters out the shorter wave radiationcomponent of λ≦280 nm. It is suitable and technically advantageous touse the entire radiation range with wavelengths above and below saidlimits.

[0014] HFC-365mfc can be purified in the liquid phase or in the gasphase. Pentachloroethane is advantageously produced in the liquid phase.CFC-112a, CFC-113a and HCFC-123 are advantageously produced in the gasphase. Continuous operation is especially facilitated by working in thegas phase.

[0015] In the gas phase, the process is advantageously conducted in aflow-through apparatus. The starting material (the correspondinghydrogen and halogen-containing starting compounds and chlorine) iscontinuously fed into the flow-through apparatus and the reactionproduct is continuously withdrawn in proportion to the amountintroduced.

[0016] The average residence time in the reaction vessel is preferablybetween 0.01 and 30 minutes, preferably between 0.01 and 3 minutes,particularly preferably between 0.5 and 3.0 minutes. Good results can beachieved even if the residence times are very short, e.g., between 0.04and 0.5 minutes. The optimum average residence time, which depends,among other things, on the lamp output and on the geometric parametersof the radiation apparatus (flow-through apparatus) can be determined bysimple manual tests and analysis of the product stream, e.g., by gaschromatography.

[0017] Better conversion rates and higher selectivity can be achieved byusing, instead of a single radiation lamp with a certain output, two ormore lower-output lamps with an equivalent total output in reactors thatare connected in series. The product is then advantageously separatedafter leaving the corresponding reactions, e.g., by freezing it out.Proper swirling of the reaction mixture, e.g., by suitable installationsin the reactor, is also often advantageous. In the liquid phase, it ispreferred to work in batches. The process has the advantages of highconversion at high selectivity.

[0018] The following examples are intended to illustrate the inventionin greater detail without limiting its scope.

EXAMPLES 1 TO 6

[0019] Production of 1,1,1-trifluoro-2,2,2-trichloroethane (CFC-113a)Through Photochlorination of 1,1,1-trifluoro-2,2-dichloroethane(HCPC-123) Through Duran 50 with Light with a Wavelength of λ>280 nm.

[0020] Apparatus: double shell glass reactor (double shell for oilheating) with a submersible shaft made of Duran® 50 (400 ml reactionvolume), equipped with a submersible Hg discharge lamp TQ 718 byHeraeus-Noblelight with water cooling. The1,1,1-trifluoro-2,2-dichloroethane was evaporated with a pre-evaporatorand was introduced from below as a gas into the reactor together withthe chlorine (mixed). The product stream exited at the top. The reactiontemperature was 110° C. The gas stream exiting the reactor was analyzedby gas chromatography (GC) (sampling in the gas collection tube). Tests1 to 6 conducted with different chlorine feeds: Test mole % ChlorineConversion Rate 113a Selectivity 1 10 3.79 99.13 2 30 5.18 99.04 3 6017.41 97.7 4 90 31.94 98.29 5 120 80.63 95.9 6 150 100 97.3

EXAMPLES 7 TO 11 (Comparison Tests)

[0021] Production of 113a by Photochlorination of 123 Through QuartzGlass

[0022] Apparatus: double shell glass reactor (double shell for oilheating) with submersible shaft made of quartz glass (400 ml reactionvolume) equipped with submersible Hg discharge lamp TQ 718 of HeraeusNoblelight with water cooling. The 1,1,1-trifluoro-2,2-dichloroethanewas evaporated and introduced from below as a gas into the reactortogether with the chlorine. The product stream exited at the top. Thereaction temperature was 110° C. Tests 1 to 5 conducted with differentchlorine feeds: Test mole % Chlorine Conversion Rate 113a Selectivity 710 1.44 96.4 8 30 13.5 95.64 9 60 13.4 90.1 10 90 26.64 93.5 11 12077.24 79.17

EXAMPLE 12

[0023] Removal of olefinic byproducts from 1,1,1,3,3-pentaflurobutane(365mfc) through photochlorination with λ>280 nm

[0024] a) Laboratory Tests

[0025] 50 g samples of 365mfc contaminated with 7,000 ppm C₄ClF₃H₄ (twoisomers) were disposed, respectively, in two 100-ml Durant 50 glassflasks and agitated.

[0026] Thermal Test:

[0027] Immediately after adding 0.4 g (5.6 mmole) chlorine, the oneflask was wrapped in aluminum foil. After 24 h the sample was examinedby gas chromatography. Out of the 7,000 ppm C₄ClF₃H₄ (2 isomers), 4,450ppm were still detected, but the 365mfc content was reduced by well over1%.

[0028] Photochemical Test:

[0029] The second flask, after adding 0.2 g (2.8 mmole) chlorine, wasirradiated overnight with a Philips fluorescent lamp (Philips reflectorlamp No. 1099415, 40 W output). Subsequently, the sample was examined bygas chromatography. Out of the 7,000 ppm C₄ClF₃H₄ (2 isomers), 160 ppmwere still detected, but the 365mfc content was almost unchanged. Afurther addition of 0.2 g (2.8 mmole) chlorine and irradiation overnightresulted in an amount of C₄ClF₃H₄ that was no longer detectable (<0.1ppm, SIM run, GS-MSD), again with a nearly constant 365mfc content.

[0030] b) Technical Test

[0031] Test setup: Pfaudler reactor (V=100 l) with mounted glass columnwith top cooler (water cooling). In the cover of the Pfaudler reactor, asubmersible Hg discharge lamp TQ 718 by Heraeus Noblelight was installedwith a submersible tube made of Duran 50 glass. Irradiation thus tookplace at a wavelength of_(—)>280 nm. The output was adjusted to 700 W.

[0032] Procedure: The 365mfc was pumped into the Pfaudler reactor. Onehalf hour prior to chlorine metering, the submersible Hg discharge lamp(700 watt) was turned on while mixing. Through a submersible tube,approximately 20 l/h of chlorine were added until no olefins could bedetected in the SIM run of the GC-MSD. After chlorination was completed,the submersible Hg discharge lamp was operated for another hour. The365mfc thus treated was discharged and precision distilled in adistillation column (height: 3 m, diameter 100 mm, filled with 10 mmRaschig glass packing).

[0033] Test 12.1:62.3 kg educt treated with 40.9 g chlorine/testduration 3 hours. GC analysis of educt (before photochlorination): 99.5w/w % 365mfc,

[0034] Total C₄ClF₃H₄: 0.112 w/w %

[0035] GC analysis of product (after photochlorination): 99.4 w/w %365mfc,

[0036] Total C₄CIF₃H₄: <10 ppm

[0037] Test 12.2: 62.0 kg educt treated with 110.9 g chlorine/testduration 5 hours.

[0038] Analysis of educt: 99.7% 365mfc,

[0039] Total C₄ClF₃H₄: 0.210%

[0040] Analysis of product: 99.6 w/w % 365mfc,

[0041] Total C₄ClF₃H₄: <10 ppm

[0042] Purification: The fractions obtained from the tests were combinedand precision distilled in the glass column. Their purity afterdistillation was 99.98% w/w % 365mfc.

EXAMPLE 13

[0043] Production of Pentachloroethane (120) from TrichloroethyleneThrough Photochlorination with λ>280 mn

[0044] a) Photochlorination Test on a 5 l Scale

[0045] Test setup: A 5 liter double shell vessel of Duran 50 glass withmounted reflux condenser, bubble counter and submersible tube withdiffuser. The vessel also contained a water-cooled cooling coil. Thevessel was irradiated from the outside with a Philips fluorescent tube(Philips reflector lamp No. 1099415, 40 Watts output).

[0046] Procedure: 3.24 kg (24.7 moles) trichloroethylene were filledinto the vessel and heated to 60° C. (thermostat, connected to doubleshell). Subsequently, 1.926 kg (27.17 moles) chlorine was metered suchthat no chlorine was penetrating through or exiting the apparatusthrough the bubble counter. The reaction was completed after 3 hours.

[0047] Purification: The resulting pentachloroethane had a 99.4% degreeof purity (rest: unconverted trichloroethylene and hexachloroethane) andcan be used without further purification.

[0048] b) Technical Photochlorination Test

[0049] Test setup: Pfaudler reactor (V=100 l) with mounted glass columnwith top cooler (water cooling). In the cover of the Pfaudler reactor, asubmersible Hg discharge lamp TQ 718 by Heraeus Noblelight was installedwith a submersible tube made of Duran® 50 glass. Irradiation thus tookplace at a wavelength of λ>280 nm. The output was adjusted to 500 Watts.

[0050] Procedure: 65.7 kg (507 mole) trichloroethylene was filled intothe Pfaudler reactor and heated to 60° C. and mixed. Subsequently, afterlighting and burning in the lamp, 35.36 kg (500.1 mole) chlorine wasintroduced such that the chlorine did not penetrate through.

[0051] Purification: At the end of the test, without any furtherpurification, the pentachloroethane produced had a degree of purity of99.1% (GC %);

[0052] remainder: trichloroethylene and hexachloroethane.

EXAMPLE 14 (COMPARISON EXAMPLE)

[0053] Thermal Chlorination

[0054] 14a) Thermal Chlorination of Trichloroethylene

[0055] 50 g (0.381 mole) trichloroethylene was combined with 28 g (0.423mole) chlorine in a 250 ml Roth autoclave and placed into an oil bathpreheated to 100° C. When an internal temperature of about 50° C. wasreached, marked exothermia developed and the autoclave content wasdischarged through the bursting disk into the outlet.

[0056] 14b) Thermal Test on a 5 Liter Scale

[0057] Test setup: A 5 liter double shell vessel of Duran 50 glass withmounted reflux condenser, bubble counter and submersible tube withdiffuser. The vessel also contained a water-cooled cooling coil. Theapparatus was completely covered with aluminum foil.

[0058] Procedure: 3.24 kg (24.7 mole) trichloroethylene was introducedinto the vessel and heated to 60° C. (thermostat, connected to doubleshell). Subsequently, 1.926 kg (27.17 mole) chlorine was metered suchthat no chlorine was penetrating through or exiting the apparatus viathe bubble counter. After 15 hours, the introduction of chlorine wascompleted.

[0059] Purification: The resulting pentachloroethane had a purity of83.3% (residue: unconverted trichloroethylene and large amounts ofhexachloroethane).

EXAMPLES 15 TO 19

[0060] Production of 1,1,1-triffluoro-2,2-dichloroethane (123) from1,1,1-trifluoro-2-chloroethane (133a) Through Photochlorination withλ>280 mn.

[0061] General Setup and Execution for Tests 15 to 19:

[0062] A mixture of 94.8 g (0.80 mole) 133a and a variable amount ofchlorine were mixed and introduced in the form of a gas into aphotochemical reactor holding 4.3 liters (diameter 100 mm, wallthickness 2 mm) made of Duran® 50. The reaction temperature during the30-minute tests was 40° C. Irradiation was effected by 3×40 W UV lampsfrom Philips, type “Cleo Performance R-UVA 40 Watts” The lamps werecylindrically arranged around the photochemical reactor. The tests wereevaluated by GC analysis of the reactor exhaust gas. Example 15: Feed:94.8 g (0.80 mole) 133a, 5.67 g (0.08 mole) chlorine Result: Conversion:13.98% Selectivity 123: 86% Selectivity 113a: 13% Example 16: Feed: 94.8(0.80 mole) 133a, 17.01 g (0.24 mole) chlorine Result: Conversion: 25.2%Selectivity 123: 74% Selectivity 113a: 26% Example 17: Feed: 94.8 (0.80mole) 133a, 34.03 g (0.48 mole) chlorine Result: Conversion: 38.8%Selectivity 123: 57.4% Selectivity 113a: 42% Example 18: Feed: 94.8(0.80 mole) 133a, 51.05 g (0.08 mole) chlorine Result: Conversion: 45.8%Selectivity 123: 47% Selectivity 113a: 53% Example 19: Feed: 94.8 (0.80mole) 133a, 68.06 g (0.96 mole) chlorine Result: Conversion: 51%Selectivity 123: 44.3% Selectivity 113a: 56%

EXAMPLE 20

[0063] Photochlorination of 142b to Produce 112a

[0064] The reaction was performed analogously to Examples 1 to 6.Conversion and yield were comparable to the results from the productionof 113a.

[0065] The foregoing description and examples have been set forth merelyto illustrate the invention and are not intended to be limiting. Sincemodifications of the described embodiments incorporating the spirit andsubstance of the invention may occur to persons skilled in the art, theinvention should be construed broadly to include all variations fallingwithin the scope of the appended claims and equivalents thereof.

What is claimed is:
 1. A process for producing a chlorine-containingalkane selected from the group consisting of pentachloroethane;1,1,1-trifluoro-2,2,2-trichloroethane and1,1,1,2-tetrachloro-2,2-difluoroethane by addition of chlorine totrichloroethylene in liquid phase to produce pentachloroethane, or byexchange of hydrogen for chlorine in gas or liquid phase to produce1,1,1-trifluoro-2,2,2-trichloroethane from1,1,1-trifluoro-2-chloroethane or 1,1,1-trifluoro-2,2-dichloroethane, orto produce 1,1,1,2-tetrachloro-2,2-difluoroethane from2,2-difluoro-2-chloroethane, or to produce purified1,1,1,3,3-pentafluorobutane from 1,1,1,3,3-pentafluorobutane that hasbeen contaminated by unsaturated compounds with C—C double bonds or C—Ctriple bonds by chlorinating the unsaturated contaminating compounds,wherein a respective starting compound is contacted with elementalchlorine and irradiated with UV light having a wavelength of λ>280 nm.2. A process according to claim 1, wherein the process is carried out inthe liquid phase.
 3. A process according to claim 1, wherein the processis carried out at a temperature in the range from room temperature to200° C.
 4. A process according to claim 1, wherein the process iscarried out at a pressure of 1 to 10 bar (absolute).
 5. A processaccording to claim 1, wherein 1,1,1,3,3-pentafluorobutane is purified byconverting unsaturated impurities into chlorine-containing impuritiesand separating the chlorine containing impurities.
 6. A processaccording to claim 1, wherein elemental chlorine is used in an amountthat is 0.9 times to 1.3 times the stoichiometrically required amount.